A number of diagnostic and interventional vascular procedures are now performed translumenally, where an elongate instrument such as a catheter is introduced to the vascular system at a convenient access location—such as the femoral, brachial, or subclavian arteries—and guided through the vascular system to a target location to perform therapy or diagnosis. When vascular access is no longer required, the catheter and other vascular access devices must be removed from the vascular entrance and bleeding at the puncture site must be stopped. One common approach for providing hemostasis is to apply external force near and upstream from the puncture site, typically by manual compression. This method is time-consuming, frequently requiring one-half hour or more of compression before hemostasis. This procedure is uncomfortable for the patient and frequently requires administering analgesics. Excessive pressure can also present the risk of total occlusion of the blood vessel, resulting in ischemia and/or thrombosis. After hemostasis is achieved by manual compression, the patient is required to remain recumbent for six to eighteen hours under observation to assure continued hemostasis. During this time bleeding from the vascular access wound can restart, potentially resulting in major complications. These complications may require blood transfusion and/or surgical intervention.
Bioabsorbable fasteners have also been used to stop bleeding. Generally, these approaches rely on the placement of a thrombogenic and bioabsorbable material, such as collagen, at the superficial arterial wall over the puncture site. This method generally presents difficulty locating the interface of the overlying tissue and the adventitial surface of the blood vessel. Implanting the fastener too far from the desired location can result in failure to provide hemostasis. If, however, the fastener intrudes into the vascular lumen, thrombus can form on the fastener. Thrombus can embolize downstream and/or block normal blood flow at the thrombus site. Implanted fasteners can also cause infection and auto-immune reactions/rejections of the implant.
Suturing methods also have used to provide hemostasis after vascular access. The suture-applying device is introduced through the tissue tract with a distal end of the device located at the vascular puncture. Needles in the device draw suture through the blood vessel wall on opposite sides of the punctures, and the suture is secured directly over the adventitial surface of the blood vessel wall to close the vascular access wound. Generally, to be successful, suturing methods need to be performed with a precise control. The needles need to be properly directed through the blood vessel wall so that the suture is well anchored in tissue to provide for tight closure. Suturing methods also require additional steps for the physician.
In view of the deficiencies of the above methods and devices, a new generation of “self-sealing” closure devices and methods has been developed to avoid the need for implantation of a prosthesis member, and also to minimize the steps and time required for closure of the vascular site. Such self-sealing configurations are available, for example, from Arstasis, Inc., of Redwood City, Calif. under the tradename Axera™, and are described in publications such as U.S. Pat. Nos. 8,083,767, 8,012,168, 8,002,794, 8,002,793, 8,002,792, 8,002,791, 7,998,169, and 7,678,133, each of which is incorporated by reference herein in its entirety.
With self-sealing and other configurations of closure devices, it may be desirable to achieve vascular access with relatively small instruments before dilation up to larger working lumens for subsequent diagnostic or interventional steps. For example, rather than starting with a Seldinger access technique wherein a needle and guidewire set configured to place a conventional 0.035″ diameter guidewire are utilized, a self-sealing access technique may be employed to place a much smaller guidewire, such as an 0.018″ diameter guidewire. With a relatively small guidewire, such as an 0.018″ diameter guidewire, in place by the Seldinger technique, a subsequent process step may be to install an introducer catheter assembly, generally comprising an introducer catheter defining an introducer lumen, and a dilator member configured to fit with in the introducer lumen. The dilator member generally will define its own dilator member lumen through which the guidewire may be threaded, to facilitate an “over-the-wire” installation of the distal portions of the introducer catheter and dilator member into the vascular lumen.
One of the challenges with an over-the-wire installation of a conventional introducer-dilator assembly over a relatively small guidewire, such as an 0.018″ diameter guidewire, is that many readily available off-the-shelf introducer-dilator sets are configured to fit more conventional guidewire diameters through the dilator member lumen, such as diameters in the range of 0.035 inches. The geometric mismatch between a 0.018″ diameter guidewire and a distal end of a dilator member sized for a 0.035″ diameter guidewire, for example, can result in what may be termed an “annular gap” that may form a mechanical edge at the interface between these structures, and insertion of this gap or edge relative to the vascular tissue to place the dilator member and associated introducer catheter distal tips within the vascular lumen may result in unwanted localized tissue trauma, heightened insertion forces, and undesirable localized stress concentrations on portions of the guidewire, dilator member, and/or introducer catheter. There is a need to address this challenge so that conventionally-sized dilator-introducer assemblies, such as those designed for 0.035″ diameter guidewires, may be more optimally utilized with relatively small guidewires, such as those having diameters in the range of 0.018 inches, which may be desirable with procedures such as self-sealing vascular access and closure procedures.